(function($) { 

    //获取id
    function $ (id)
    {
    return typeof id === "string" ? document.getElementById(id) : id;
    }
    //获取tagName
    function $$ (elem, oParent)
    {
    return (oParent || document).getElementsByTagName(elem);
    }
    //获取class
    function $$$ (className, oParent)
    {
    var aClass = [];
    var reClass = new RegExp("(//s|^)" + className + "($|//s)");
    var aElem = $$("*", oParent);
    for (var i = 0; i < aElem.length; i++) reClass.test(aElem[i].className) && aClass.push(aElem[i]);
    return aClass
    }
    //初始化对象
    function Roll ()
    {
    this.initialize.apply(this, arguments)
    }
    Roll.prototype =
    {
    initialize: function (obj)
    {
    var _this = this;
    this.obj = $(obj);
    this.oUp = $$$("up", this.obj)[0];
    this.oDown = $$$("down", this.obj)[0];
    this.oList = $$$("list", this.obj)[0];
    this.aItem = this.oList.children;
    this.timer = null;
    this.iNow = 0;
    this.iHeight = this.aItem[0].offsetHeight;
    this.oUp.onclick = function ()
    {
    _this.up()
    };
    this.oDown.onclick = function ()
    {
    _this.down()
    }
    },
    up: function ()
    {
    this.oList.insertBefore(this.aItem[this.aItem.length - 1], this.oList.firstChild);
    this.oList.style.top = -this.iHeight + "px";
    this.doMove(0)
    },
    down: function ()
    {
    this.doMove(-this.iHeight, function ()
    {
    this.oList.appendChild(this.aItem[0]);
    this.oList.style.top = 0;
    })
    },
    doMove: function (iTarget, callBack)
    {
    var _this = this;
    clearInterval(this.timer)
    this.timer = setInterval(function ()
    {
    var iSpeed = (iTarget - _this.oList.offsetTop) / 5;
    iSpeed = iSpeed > 0 ? Math.ceil(iSpeed) : Math.floor(iSpeed);
    _this.oList.offsetTop == iTarget ? (clearInterval(_this.timer), callBack && callBack.apply(_this)) : _this.oList.style.top = iSpeed + _this.oList.offsetTop + "px"
    }, 30)
    }
    };
    window.onload = function ()
    {
    new Roll("box");
    };
})(jQuery);  